Bicking a Black Molly or Neon

I can't obtain the answer (5/6) to this question.

Four species of fish--BM, G, GF, and N-- are available in a fish store:. A child has been told that she may choose any two of these fish species for her aquarium. Then several fish of each species will be purchased. Suppose that she is equally likely to chooses each species.

I can't obtain the answer (5/6) to this question.
Four species of fish--BM, G, GF, and N-- are available in a fish store:. A child has been told that she may choose any two of these fish species for her aquarium. Then several fish of each species will be purchased. Suppose that she is equally likely to chooses each species.
She has either a BM or a N but not both.

Why do you think the answer is
There are six ways to pick two species.
Here are the outcomes you want: .
There are four not five.